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Immature grape embryos from early ripening genotypes of Vitis vinifera were successfully cultured in vitro on Difco orchid agar or a modified White's agar medium. Germination was increased in vitro for five genotypes from 0%, 7%, 11%, 12%, and 16% in vivo to 15%, 24%, 23%, 34%, and 24%, respectively. Subculturing embryos onto liquid culture from seeds that failed to germinate on agar also was possible. Differences in germination rates, as affected by pollen, were significant. This method will allow accelerated development of early ripening cultivars by allowing breeders to use such genotypes as females, as well as males.

The importance of rapid, nondestructive, and accurate measurements of leaf area (LA) in agronomic and physiological studies is well known, but a search of the literature revealed little information available for grape (Vitis vinifera L.). The results described herein include a comparison of 12 different mathematical models for estimating leaf area in `Cencibel'. The simplest, most accurate regression equations were: LA_i = 0.587 LW (R ² = 0.987) and LA_i = 0.588 LW (R ² = 0.994), where LA_i is leaf area measured using image analysis and LW is leaf length × maximum width. Use of maximum width (W), leaf length (L), petiole length (L_p), and dry weight of leaves (DML) as single variables in the regression equations were not as closely associated with total leaf area, although their R ² values were also highly significant.

Transgenic grape plants were regenerated from somatic embryos derived from leaves of in vitro-grown plants of `Thompson Seedless' grape (Vitis vinifera L.) plants. Somatic embryos were either exposed directly to engineered Agrobacterium tumefaciens or they were bombarded twice with 1-μm gold particles and then exposed to A. tumefaciens. Somatic embryos were transformed with either the lytic peptide Shiva-1 gene or the tomato ringspot virus (TomRSV) coat protein (CP) gene. After cocultivation, secondary embryos proliferated on Emershad/Ramming proliferation (ERP) medium for 6 weeks before selection on ERP medium containing 40 μg·mL^-1 kanamycin (kan). Transgenic embryos were identified after 3 to 5 months under selection and allowed to germinate and develop into rooted plants on woody plant medium containing 1 μm 6-benzylaminopurine, 1.5% sucrose, 0.3% activated charcoal, and 0.75% agar. Integration of the foreign genes into these grapevines was verified by growth in the presence of kanamycin (kan), positive β-glucuronidase (GUS) and polymerase chain-reaction (PCR) assays, and Southern analysis.